Composite radio frequency inductance



Nov. 9, 1948. J. w. MANN ET AL 2,453,241

COMPOSITE RADIO FREQUENCY INDUCTANCE Filed July 31, 1944 2 Sheets-Sheet 1 IN V EN TORS I a] GEORGE F. RUSSELL I J LIUS W MANN ATTORNEYS Nov. 9, 1948. J. w. MANN ET AL 2,453,241

COMPOSITE RADIO FREQUENCY INDUCTANCE Filed July 31, 1944 V 2 Sheets-Sheet 2 .INVENTOR. GEORGE. F. RUSSELL.

JULIUS W. MANN ATTORNEYS Patented Nov. 9, 1948 OFFICE COMPOSITE RADIO FREQUENCY I INDUCTANCE Julius W. Mann and George F. Russell, Tacoma, Wash.

Application July 31, 1944, Serial No. 547,440

The present invention relates to improvements in a composite radio frequency inductance, and it consists of the combinations, constructions and arrangements hereinafter described and claimed.

This application. is a continuation-in-part of our copending application for a Composite radio frequency inductance, Serial No. 451,064, filed July 15, 1942, now abandoned.

An object of our invention is to provide a composite radio frequency inductance that is especiall designed to be used in our Single standing wave radio circuit copending application, Serial No. 510,566, filed November 16, 1943. In the Radio circuit case, we set forth a particular arrangement of a plate, grid and output circuits which the current antinodal positions of all three circuits to coincide at a common center point in the composite inductance. The physical means i or accomplishing this is illustrated, described and claimed in the present case.

The advantage of causing the three circuits to have their current antinodal positions at a common center point on the composite inductance is to permit the radio circuit to be tuned throughout a wide range of frequencies without a resulting loss in stability which is many times the case where the current antinodal positions of the three circuits are not held at a common point.

The plate circuit has its coil physically separated from the coil of the combined grid output circuit by air or other'insulating means. The number of turns or loops of the grid output circuit coil maybe changed in accordance with the I operating wave lengths of the circuit. At high frequencies the coil may be only a portion of one turn, while at lower frequencies the coil may have many turns. The composite radio frequency inductance is simple in construction and provides an effective means for bringing the coupling current antinodal positions of all the circuits to a common point at the center of the composite inductance. The two components of the inductance may extend in a straight line rather than be coiled.

Other objects and advantages will appear in the following specification, and the novel features of the device will be particularly pointed out in the appended claims.

Our invention is illustrated in the accompanying drawings forming a part of this application, in which:

Figure 1 is a perspective view of the composite radio frequency inductance shown diagrammatically connected to a radio circuit;

Figure 2 is a wiring diagram of one type of 4 Claims. (Cl. 175-359) 2 radio circuit in which our invention may be used;

Figure 3 is a section along the line 33 of Figure 1;

Figure 4 shows the two components of the inductance straightened out and separated by an air gap; and

Figure 5 illustrates another circuit modification using straight line inductances separated by air.

In carryin out our invention we will first describe the radio circuit in which the composite radio frequency inductance is used and then the construction of the inductance itself. The radio circuit shown in Figure 2 is the same as Figure l of our copending application, Serial No. 510,566. A brief description will be given. The plate circuit is indicated generally at A and comprises plates I in radio tubes T l and T2, an inductance coil LI, and a variable condenser 2 which is shunted across the inductance coil. The plate leads 3 are crossed.

The grid circuit is indicated generally at B and comprises grids 4, protective condensers 5, and resistances 6. An output, pick-up or work circuit, indicated generally at C, has an inductance coil L2 which is inductively coupled to the coil Ll. The circuit C also has inductance extremities 1 and 8 with adjustable leads 9 and [0 connected to plates 1 l and 12 between which the work W is placed. It will be noted that the leads l3 and [4 of the grid circuit B are adjustably connected to the extremities I and 8 so that the grid and output circuits are physically the same for a portion of their lengths. v

The inductance coils Ll and-L2 are indicated diagrammatically in the radio circuit of Figure 2. In Figures 1 and 3 the physical construction of the two coils is shown. The combined grid output circuit coil L2 comprises a tube I5 that has only one half a loop formed therein. As already stated, the tube could have one or more loops formed therein according to the frequency of radio circuit used and the tube may be solid if desired. The portion of the tube [5 that is formed into one half a loop is covered by an insulating sleeve of rubber [6. Around the rubber sleeve we mount a tubular member I! that has a half turn formed therein. The coil Ll has a number of loops and has its mid portion physically connected to the tube I! at I8. The physical connection is such that a center point K of the coil Ll will be at the center of the tube I! which in turn will be at the center of the half loop of the coil L2. The midpoint K of the coil L2 will be entirely enclosed by the rubber sleeve [6 which in turn is entirely enclosed by the tube H. In this way the center of the two coils are placed. in concentric relation with the sleeve it; insulating the two centers from each other. Figures 3 show the central portion of tube i which is formed into the half loop L2 and further illustrates the insulating sleeve l6 and the external tube ll. The wireiii-leading from the. center of the tube H connectswith the B+ source of'current.

As stated above mid point K in the inductance shown in Figure 1 of the drawings is entirely enclose-d by rubber sleeve 16, which inturn isentirely enclosed by tube ll. clearly in that connection that a center tap from the coil L2 running inside of the outer tube I? may be taken out at point K without disturbing the meaning of this specification. A center connection on L2 could be either for inserting resistance to control oscillations or to groundsame through a grid resistance, thereby changing the gri-dreturn. system shown. in Figure .2.

The inductances Li and L2 are designed to have a minimum capacitive coupling between the coils at their voltage antinod'es, or in other words, where'the voltage. is high relative to the center point, of. the. respective inductances. (coupling current antinodes). This is accomplished by the grid output circuit coil Lt following the plate tank will Li, to. only. a. limited. physical distance and bringin the leads. away. from the capacitive relationship soastoreduce the effect of such capaoiti-Ve-. coupling. The closest possible coupling at the coupling current. antinodes most riearl-y approaches the ideahposition. of re1ationship for the transierofeneryand this is shown ineil'igure. 1. The. coupling current. antinodal position.iorf-all threecircuits. is. shown at K in this figure, iThasame; variable capacity used for tuningina close-coupling will; cover a range over twice that covered bit-the: sarne variable capacity with a loose coupling between, theinductances Isl and-L2 The: closer thetwo coils Ll. and- L2 approach 100%. mutual inductive v coupling, the greater'becomes the range; covered by a given variable tunin device in; the dominant circuit.

We haveshown-a self,-e xc lte,doscillator in Figurez-wihe the plate tank circuit is the-dominant one. We donotwish to-be con-fined to any one or the;.three circuits as. being the dominant one. am ne s-of ar e ve uthes id circuit may be thadominant. and then; theplate. circuit can have-a coil W oh Willgbd concentric to the grid circuit coil vfor: aportion i its distance. The wire or tube forming the coil-for; the grid-circuit may be placed; within atubular wireor outside of the wire coil constituting. the plate inductance. The distance that; the. coil of the dominant circuit runs concentric tothe coil of he other circuit or circuits; with which it is inductively coupled is basedontthe operating wavelengths ofthe circuit and/on the'constantsthereof. As already stated, high frequencies-the coil may consist ofonly a portionof; a turn or-loopwhile at: lower frequencies it may comprise; many turns or loops.

In.Figures- 4 and 5 weshcw. a modifiedform of the; composite. radio frequency inductance; In both figures the inductance. is, com posed of two concentric tubes with air as th e insulatonbe-tween the-tubes insteao ofxrubher. or; other artificial insulation. Figured iliustrates an innertube ind c an ez i e n onnect -i the g d circuit B iand the;Worlccirouit C. The rid cirouit B has leads i3; and Hi adjustably connected to the virs i' udfiefth o c cuit by t ps 1.! and 2- T-he outer; concentric-flube constitutes an in Let it be pointed out ductancc L4 and this tube is insulated from the inner tube L3 by air and forms a part of the plate circuit A. The 33-}- current is connected to the tube Le at K while the center of the tube L3 is tapped at K by a lead 23 that connects with a resistance 24 and the resistance is grounded at 25. The plates l of the tubes TI and T2 are interconnected by a. variablecondenserZ. It will be noted fromFi-gure 4 that the grid blocking condensers 5 shown in Figure l, are not used in the radio circuit disclosed in Figure 4. Both in- I ductanoes L3 and L4 are center tapped.

The operation of this form of the invention is the same as that shown in Figure 2. The important relationship of the inductances to the various circuits is that the mutual inductance of the two component parts L3 and L l extend for equal distances on either side of their coinciding center points K and K. By this we mean that the two inductances extend coaxially, as set forth in Figure 3 and th eir coaxialportions are small in. proportion to their total respective lengths. The coaxial, member L3 constitutes the center portion of the rid circuit and the coaxial portion L l constitutes the central portion of, the plate circuit.

The electrostatic strain under conditions. of radio frequency energy are such as to puncture the most defective part of any insulating means placed between thetwo concentric membersL3 and L4 of the mutual inductance. Once thisinsulatingmeans ispunctured, if itis made o frub or. other insulating. material, nothing can. be donebutremove it andsubstitutea new. one. If

air is-used as insulation as shown in Figure};

and an arc should occur between the. inductances; the air is self-healing; and; after the... are 1516;? tinguis ed the inductance. can be: used. as before aany. change. For this reason air is shown as the insulation used in Figure. 4.

It makes little differencewhether the inductance isshapedlilma coil, as inEigure-l; or whether it .is in straight tubes, asshown in Fig.- ures; 4; and; salons as; the; coaxial relationship of'the two inductances: covers v a sufficientdistance. either side; of their, respective center points. to give the. mutual inductance the; r e-.- quired stability, If the; mutual V inductance 1 00V: pling is too short in relation to-the total length of the two inductances, the tendency will be. towarddess mutual. inductance and; a. decreasing. deg-rec of stability ofthe oscillating unit. Should the mutual coaxial relationshipbe too long with reference: tothe total: length ofthe inductances, instability, would, again result and the advantages. of'this type of mutual. coupling lost.

In- Figure 5 the innerv tuba inductance. L3 is: connected to the plate circuit Al, rather than tothe grid circuit Thetouter tube-inductance L4.

isconnected to the grid circuit B. In all other. respects the wiring-of thecircuit of Figure 5- is the same as that of Figure l'; therefore-like reference numerals will be applied to similar parts. From the circuits shown-in Figures 4 and 5; it will be apparentthatthe grid circuitportion of the inductance can either be the inside. or the u e membe of. the, a ia .v du ta Again the. important relationship, between the. two inductances is the mutual inductance o f -the v two component, parts, for equal. distances either side of their coinciding center; points, the coaxial portions of the inductances. being small when onsi e n he i tal. e th We claim:

1. In a composite radio frequency inductance, a conduit having a coiled portion, an insulating sleeve enclosing the conduit, a metal sleeve conduit enclosing the insulating sleeve, and a third conduit having a coiled portion with its central part physically connected to the metal sleeve.

2. In. a composite radio frequency inductance, a conduit formed in a coil for carrying radio frequency waves, an insulating sleeve enclosing at least the central portion of the conduit, a second conduit for carrying radio frequency waves and enclosing at least the central portion of the insulating sleeve, and a second coil having its central portion physically connected to the central portion of the second conduit, the first and second coils extending substantially coaxially with each other to equal distances on both sides of the common center point for both coils, the total distance of the coaxial arrangement of the two conduits being less than a major part of their respective total lengths.

3. A mutual inductance comprising two separate inductance means coaxially related for a limited distance next to their respective coinciding center points, the extremities of the two inductances departing from such coaxial relation- 6 ship, and the coaxial relationship of the two inductances adjacent to their coinciding centers existing to an extent of less than 50% of the total length of each separate inductance means. a. A composite radio frequency inductance comprising an inductance having at least a partial loop formed therein, an insulating sleeve enclosing the partial loop, a conductor sleeve enclosing the insulating sleeve, and a second inductance having a plurality of loops, the midpoint of the second inductance being physically connected to the midportion of the conductor sleeve.

JULIUS W. MANN. GEO. F. RUSSELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,865,840 Croft July 5, 1932 1,891,481 Scofield Dec. 20, 1932 2,149,387 Brown Mar. 7, 1939 2,348,325 Brown May 9, 1944 

